Procedures will be developed by which consistently high proportions of rhesus (Macaca mulatta) oocytes can be fertilized in vitro. Fertilized oocytes will be cultured for several days in order to permit study of preimplantation stages of development. The normality of fertilization will be assessed by morphological and developmental criteria, and ultimately by ability of fertilized oocytes to develop into full-term off-spring. In vitro fertilized embryos will be transplanted into recipient monkeys in order to establish pregnancy, which will be closely monitored. The primary objective of this investigation is to assess the reproducibility and effectiveness of primate in vitro fertilization procedures in order to provide an exprimental basis for predicting the incidence, nature and degree of developmental abnormalities, if any, associated with these techniques when applied to humans. Rhesus offspring resulting from in vitro fertilization will be closely monitored and evaluated for evidence of morphological, behavioral, mental, learning and psychosexual anomalies, using existing data on these parameters for comparative purposes.